Ammonia-nitrogen (NH4+/NH3) is one of the important nutrients which derive from biological wastewater treatment. Direct ammonia oxidation has been studied as the anolyte in an ammonia-fed fuel cell system. This work synthesized an effective AgO/Ag2O/rGO electrode for oxidizing NH3. The electroplating of Ag and rGO was conducted under 3V for 5 min, followed by calcination at 400 oC for 2 h in an Ar atmosphere. Batch constant current experiments were carried out to assess the performance of AgO/rGO as the anode. The voltammetry evidenced that the rGO layer significantly improved the electrical capacitance of the mixed-phase of AgO/Ag2O which played the role of electron mediator. Accordingly, on Ag sites, NH3 was dehydrogenated irreversibly via direct electron transfer; nonetheless, the reversible oxygenation of ammonia was catalytically performed by the phase transformation of AgO to Ag2O. AgO/rGO was effective in NH3 removal (R = 100%). However, the concentration of NO2-/NO3- produced on the Ag electrode was about four times higher than those on Ag/rGO, due to the excess of OHads species formed on Ag at lower potentials.

Catalytic characteristic of silver oxide intercalated reduced graphene oxide (AgO/Ag2O/rGO) in electrooxidation of ammonia

ACS Spring 2022

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